A RIGOROUS COMPARISON OF METHODS FOR MULTI-WALLED CARBON NANOTUBES PURIFICATION USING RAMAN SPECTROSCOPY

Multi-walled carbon nanotubes (MWNT’s) were synthesized using chemical vapor deposition (CVD) method in a fluidized bed reactor under the flow of methane and hydrogen gases. A Cobalt-molybdenum/magnesium oxide (Co-Mo/MgO) nanocatalyst was used as the catalyst of the process. The samples were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The effects of different combinations of purification methods, including oxidation, HCl treatment, and HNO3 treatment and the sequence of performing these methods on the quality of the carbon nanotubes are discussed. Raman spectroscopy with a laser excitation of 532 nm was utilized as the measurement tool. The results provide the best purification methods of synthesized carbon nanotubes. The IG/ID ratio for the optimum sample is equal to 1.28. Moreover, as another application of Raman analysis results, the apparent Young’s modulus of MWNT’s was calculated by the use of intensity ratio ID/IG. As expected, the optimum sample had the highest apparent Young’s modulus of 40459.85 MPa.